must_not_suspend impl

compiler/rustc_feature/src/active.rs

@@ -679,6 +679,10 @@ declare_features! (
     /// Allows `let...else` statements.
     (active, let_else, "1.56.0", Some(87335), None),
 
+    /// Allows `#[must_not_suspend]`.
+    (active, must_not_suspend, "1.56.0", Some(83310), None),
+
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------

compiler/rustc_feature/src/builtin_attrs.rs

@@ -202,6 +202,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ungated!(forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
     ungated!(deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
     ungated!(must_use, Normal, template!(Word, NameValueStr: "reason")),
+    gated!(
+        must_not_suspend, Normal, template!(Word, NameValueStr: "reason"), must_not_suspend,
+        experimental!(must_not_suspend)
+    ),
     // FIXME(#14407)
     ungated!(
         deprecated, Normal,

compiler/rustc_lint/src/lib.rs

@@ -298,6 +298,7 @@ fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
         UNUSED_LABELS,
         UNUSED_PARENS,
         UNUSED_BRACES,
+        MUST_NOT_SUSPEND,
         REDUNDANT_SEMICOLONS
     );
 

compiler/rustc_lint_defs/src/builtin.rs

@@ -314,6 +314,13 @@ declare_lint! {
     "imports that are never used"
 }
 
+declare_lint! {
+    /// [the reference]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute
+    pub MUST_NOT_SUSPEND,
+    Warn,
+    "Use of a `#[must_not_suspend]` value across a yield point",
+}
+
 declare_lint! {
     /// The `unused_extern_crates` lint guards against `extern crate` items
     /// that are never used.
@@ -2993,6 +3000,7 @@ declare_lint_pass! {
         CENUM_IMPL_DROP_CAST,
         CONST_EVALUATABLE_UNCHECKED,
         INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
+        MUST_NOT_SUSPEND,
         UNINHABITED_STATIC,
         FUNCTION_ITEM_REFERENCES,
         USELESS_DEPRECATED,

compiler/rustc_passes/src/check_attr.rs

@@ -104,6 +104,7 @@ impl CheckAttrVisitor<'tcx> {
                 sym::default_method_body_is_const => {
                     self.check_default_method_body_is_const(attr, span, target)
                 }
+                sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target),
                 sym::rustc_const_unstable
                 | sym::rustc_const_stable
                 | sym::unstable
@@ -1014,6 +1015,21 @@ impl CheckAttrVisitor<'tcx> {
         is_valid
     }
 
+    /// Checks if `#[must_not_suspend]` is applied to a function. Returns `true` if valid.
+    fn check_must_not_suspend(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
+        match target {
+            Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => {
+                self.tcx
+                    .sess
+                    .struct_span_err(attr.span, "`must_not_suspend` attribute should be applied to a struct, enum, `impl Trait`, or `dyn Trait`")
+                        .span_label(*span, "is a function")
+                        .emit();
+                false
+            }
+            _ => true,
+        }
+    }
+
     /// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid.
     fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
         match target {

compiler/rustc_span/src/symbol.rs

@@ -836,6 +836,7 @@ symbols! {
         mul,
         mul_assign,
         mul_with_overflow,
+        must_not_suspend,
         must_use,
         mut_ptr,
         mut_slice_ptr,